MACOSX_DEPLOYMENT_TARGET keeps reverting to old values

Question

I'm trying to build a Flutter app that targets macOS. After adding some dependencies, like just_audio, I am given warnings regarding MACOSX_DEPLOYMENT_TARGET in various locations being set to various values which need to be changed to some other value.

So, I open Xcode and studiously set the values as instructed. After that the app compiles successfully without warnings and performs as expected once, twice, maybe even three times, but inevitably the warnings will return. When I go back into Xcode I find that all of the values have reverted back to what they were before. I've tried different target versions, from 10.15 up to 13.1 (currently installed), but the warnings always come back eventually.

Am I missing an important step? I'm not new to software development, but I am completely new to macOS and Xcode.

Here's a sample of the errors that keep coming back:

Launching lib/main.dart on macOS in debug mode...
--- xcodebuild: WARNING: Using the first of multiple matching destinations:
{ platform:macOS, arch:arm64, id:00006000-000210D03EB8401E }
{ platform:macOS, arch:x86_64, id:00006000-000210D03EB8401E }
/Users/foo/projects/just_audio_background_test/macos/Pods/Pods.xcodeproj: warning: The macOS deployment target 'MACOSX_DEPLOYMENT_TARGET' is set to 10.6, but the range of supported deployment target versions is 10.13 to 13.1.99. (in target 'FMDB' from project 'Pods')
/Users/foo/projects/just_audio_background_test/macos/Pods/Pods.xcodeproj: warning: The macOS deployment target 'MACOSX_DEPLOYMENT_TARGET' is set to 10.11, but the range of supported deployment target versions is 10.13 to 13.1.99. (in target 'sqflite' from project 'Pods')
/Users/foo/projects/just_audio_background_test/macos/Pods/Pods.xcodeproj: warning: The macOS deployment target 'MACOSX_DEPLOYMENT_TARGET' is set to 10.11, but the range of supported deployment target versions is 10.13 to 13.1.99. (in target 'audio_session' from project 'Pods')
/Users/foo/projects/just_audio_background_test/macos/Pods/Pods.xcodeproj: warning: The macOS deployment target 'MACOSX_DEPLOYMENT_TARGET' is set to 10.12.2, but the range of supported deployment target versions is 10.13 to 13.1.99. (in target 'audio_service' from project 'Pods')
/Users/foo/projects/just_audio_background_test/macos/Runner.xcodeproj: warning: The macOS deployment target 'MACOSX_DEPLOYMENT_TARGET' is set to 10.11, but the range of supported deployment target versions is 10.13 to 13.1.99. (in target 'Flutter Assemble' from project 'Runner')
/Users/foo/projects/just_audio_background_test/macos/Pods/Pods.xcodeproj: warning: The macOS deployment target 'MACOSX_DEPLOYMENT_TARGET' is set to 10.11, but the range of supported deployment target versions is 10.13 to 13.1.99. (in target 'FlutterMacOS' from project 'Pods')

Here's my flutter doctor output:

[✓] Flutter (Channel stable, 3.3.10, on macOS 13.1 22C65 darwin-arm, locale en-TW)
[✓] Android toolchain - develop for Android devices (Android SDK version 33.0.0)
[✓] Xcode - develop for iOS and macOS (Xcode 14.2)
[✓] Chrome - develop for the web
[✓] Android Studio (version 2021.3)
[✓] VS Code (version 1.74.1)
[✓] Connected device (2 available)
[✓] HTTP Host Availability

Answer 1

The reason is because flutter will perform pod install when you try to run or build. So edit your post_install in Podfile like below. The code added will force the deployment target to 10.13 when flutter executes pod install.

post_install do |installer|
  installer.pods_project.targets.each do |target|
    flutter_additional_macos_build_settings(target)
    target.build_configurations.each do |config|
      config.build_settings['MACOSX_DEPLOYMENT_TARGET'] = '10.13'
    end
  end
end

Full Example is below

platform :osx, '10.13'

# CocoaPods analytics sends network stats synchronously affecting flutter build latency.
ENV['COCOAPODS_DISABLE_STATS'] = 'true'

project 'Runner', {
  'Debug' => :debug,
  'Profile' => :release,
  'Release' => :release,
}

def flutter_root
  generated_xcode_build_settings_path = File.expand_path(File.join('..', 'Flutter', 'ephemeral', 'Flutter-Generated.xcconfig'), __FILE__)
  unless File.exist?(generated_xcode_build_settings_path)
    raise "#{generated_xcode_build_settings_path} must exist. If you're running pod install manually, make sure \"flutter pub get\" is executed first"
  end

  File.foreach(generated_xcode_build_settings_path) do |line|
    matches = line.match(/FLUTTER_ROOT\=(.*)/)
    return matches[1].strip if matches
  end
  raise "FLUTTER_ROOT not found in #{generated_xcode_build_settings_path}. Try deleting Flutter-Generated.xcconfig, then run \"flutter pub get\""
end

require File.expand_path(File.join('packages', 'flutter_tools', 'bin', 'podhelper'), flutter_root)

flutter_macos_podfile_setup

target 'Runner' do
  use_frameworks!
  use_modular_headers!

  flutter_install_all_macos_pods File.dirname(File.realpath(__FILE__))
end

post_install do |installer|
  installer.pods_project.targets.each do |target|
    flutter_additional_macos_build_settings(target)
    target.build_configurations.each do |config|
      config.build_settings['MACOSX_DEPLOYMENT_TARGET'] = '10.13'
    end
  end
end

Answer 2

A more robust solution than the answer above is this:

post_install do |installer|
  # Ensure pods also use the minimum deployment target set above
  # https://stackoverflow.com/a/64385584/436422
  puts 'Determining pod project minimum deployment target'

  pods_project = installer.pods_project
  deployment_target_key = 'MACOSX_DEPLOYMENT_TARGET'
  deployment_targets = pods_project.build_configurations.map{ |config| config.build_settings[deployment_target_key] }
  minimum_deployment_target = deployment_targets.min_by{ |version| Gem::Version.new(version) }

  puts 'Minimal deployment target is ' + minimum_deployment_target
  puts 'Setting each pod deployment target to ' + minimum_deployment_target

  installer.pods_project.targets.each do |target|
    flutter_additional_ios_build_settings(target)
    target.build_configurations.each do |config|
      config.build_settings[deployment_target_key] = minimum_deployment_target
    end
  end
end

Based on this answer to a similar question for iOS.